The past five years of Smokey's life have been unbearable. Her owner recalls when her once playful and curious kitty's behavior changed.

"It was the summer of 2011. I noticed that she started hiding and that she wasn't as social and then I noticed that her mouth was giving her problems," said Gail Salisbury. 

A trip to the vet confirmed that Smokey had feline chronic gingivostomatitis or FCGS, a painful inflammatory mouth disease.

"Chronic stomatitis is a common disease in the cat. It is very debilitating. Those cats are in great pain and it is a very enigmatic disease because no one has been able to reproduce it in experimental cats," said Dr. Frank Verstraete, a professor of dentistry and oral surgery at the University of California, Davis.

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Without being able to reproduce the disease, researchers have no idea what causes it or how to effectively treat it. Cats with FCGS usually have all their teeth removed, clearing up the inflammation in some but not all cases.

Smokey wasn't lucky. Her teeth were extracted but the disease persisted. That's when she was enrolled in a clinical trial.

"We are tackling what we call the hard core population of cats. They have had extractions. Many of them have been on steroid treatment for a long time. Some even came with early diabetes so they can't get steroids anymore," said Dr. Boaz Arzi, an assistant professor of dentistry and oral surgery. 

Researchers used stem cells derived from their feline patients with the hope of reducing inflammation and promoting tissue regeneration.

"I would say that most of our cats, if I have to give a number 60 to 70 percent have responded favorably to the treatment either by complete resolution or substantial clinical improvement without complete resolution at six months," said Arzi. 

A higher percentage of cats showed signs of recovery after six months, as was the case with Smokey, who began responding to the treatment more than a year after she was injected withstem cells.

The researchers say these trials are shedding light on these types of inflammatory diseases - and that could potentially have significant implications for humans.

"There are two other species that can get chronic inflammation of the mouth. The first one is the dog and obviously we would like at treatment for dogs as well, but even more importantlyhumans also get inflammation of their oral cavity," said Verstraete. 

There are plans for human trials using stem cell therapy to treat inflammatory mouth disease as early as next year at UC Davis.

As for Smokey, she's cured, but is in need of a diet. Her owner doesn't think so.  

"She has been through enough, whatever she wants she can have."